1. Field of the Invention
The present invention relates to a magnetic recording medium, and more particularly, it relates to a ferromagnetic metal thin film recording medium having excellent reliability.
2. Description of the Related Art
In general, widely used is a magnetic recording medium which is produced by applying a magnetic paint containing a dispersed magnetic powder such as an oxide powder (e.g. .gamma.-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4, an intermediate oxide of .gamma.-Fe.sub.2 O.sub.3 and Fe.sub.3 O.sub.4, Co-modified .gamma.-Fe.sub.2 O.sub.3 and Co-modified Fe.sub.3 O .sub.4, CrO.sub.2, Ba ferrite, etc.), a metal powder (e.g. Fe, Co, etc.), alloy powder (e.g. Fe-Ni-Cr, etc.) or a nitride powder (e.g. iron nitride, etc.) and an organic binder resin such as a polyurethane resin, a polyester resin or a vinyl chloride resin on the substrate and drying the magnetic paint to form a magnetic layer.
A ferromagnetic metal thin film recording medium is considered a high magnetic recording density medium, because it is easy to achieve a high coercive force of a thin film magnetic layer in comparison with the coating type magnetic medium.
Recently, with a request for a high magnetic recording density in the ferromagnetic metal thin film recording medium field, the thin film ferromagnetic metal thin film recording medium, which comprises a ferromagnetic metal thin film formed on a substrate, such as a polyester film or a polyimide film produced by metal plating or vapor deposition such as vacuum deposition, sputtering and ion plating, has attracted considerable attention and put to practical use.
However, as the ferromagnetic metal film does not include a binder or has too good of a surface smoothness, the durability and running stability of the magnetic medium is not excellent. To solve such a problem, it is proposed to use an ester lubricant as a protective layer on the surface of the ferromagnetic metal thin film (cf. Japanese Patent Kokai Publication Nos. 85427/1985, 236118/1987 and 210615/1990).
Under the present circumstances, however, the use of the ester lubricant with the ferromagnetic metal thin film does not prevent contamination of the magnetic head or drop-out of signal efficiency.